Wine is the product of the growth and metabolism of yeasts and bacteria in grape must. It is well known that many of these and other bacteria survive all of the steps of wine making from the mature grape through vinification to bottle corking (Ribereau-Gayon (1985) “New developments in wine microbiology” Am. J. Enol. Vitic. 36:1-10). One class of organisms of interest is Acetobacter, a bacteria responsible for oxidizing ethyl alcohol into vinegar or acetic acid (Fleet and Drysdale (1988) “Acetic acid bacteria in winemaking: a review” Am. J. Enol. Vitic. 39:143-154; Lonvaud-Funel and Millet (2000) “The viable but non-culturable state of wine micro-organisms during storage” Lt. Appl. Microbiol. 30:136-141). Although present in most wines, Acetobacter does not typically generate enough acetic acid to spoil wine during bottle storage due to a lack of oxygen. As long as the wine is stored in an anaerobic environment, conditions ensured by quality corking, acceptably low quantities of acetic acid (e.g., below sensory levels) are produced and the quality of the wine is preserved. Unfortunately, the sealing performance of wine corks can degrade with age, and the long term behavior of low quality natural corks and synthetic stoppers is not well documented. One consequence of a leaky cork is the admission of oxygen to wine, a triggering of Acetobacter function, and the production of acetic acid. Furthermore, the admission of oxygen into the bottle in the presence of heat can lead to oxidation of ethanol into aldehydes. These processes lead to changes in odor and flavor, and therefore spoilage, of fine wines.
Current methods for identifying acetic acid in wine are very sensitive, detecting roughly 50 μg/L acetic acid, even though the accepted spoilage limit of acetic acid in wine is 1.4 g/L (see, for example, Kellner et al. (1998) “High performance liquid chromatography with real-time Fourier-transform infrared detection for the determination of carbohydrates, alcohols and organic acids in wines” J. Chromatogr. A. 824:159-167;Garcia-Martinet al. (2000) “Simultaneous determination of organic acids in wine samples by capillary electrophoresis and UV detection: optimization with five different background electrolytes” J. High Resol. Chromatogr. 23:647-652; Kellner et al. (1998) “A rapid automated method for wine analysis based upon sequential injection (SI)-FTIR spectroscopy” Fresenius 362:130-136; and Margalith (1981) in Flavour Microbiology, pp. 167-168, Charles Thomas Publishers, Springfield, Ill.). In addition, nuclear magnetic resonance (NMR) spectroscopy has been employed for wine fingerprinting studies and trace amino acid and organic molecule detection in wine (Guillou and Reniero (1998) “Magnetic resonance sniffs out bad wine” Physics World 11:22-23; and Kidric et al. (1998) “Wine analysis by 1D and 2D NMR spectroscopy” Analysis 26:97-101). However, all published NMR studies of wine involve removal and analysis of small volume samples of wine (e.g., less then 1 mL) to accomplish these measurements. As such, all of the current strategies for contaminant (e.g., acetic acid) detection require the bottle to be violated, a process that destroys the cork, seal, and label, severely devaluing both the wine and bottle. The present invention overcomes these and other problems by providing methods and devices for the detection of contaminants in wine bottles by NMR spectroscopy. These methods are equally applicable to other sealed consumables containers for which contamination, degradation, or other changes in product flavor or quality is a concern.